Page 19 - Geoffrey Budworth, Jason Dalton "The Little Book of Incredibly Useful Knots"

Backing up knots

Most knots (such as this square knot) will gain considerable security and strength when a simple

backup is placed around the standing end, using the working end. A backup should be used
whenever large weights or safety are a concern.

You can use a simple overhand knot (see page 292) as a backup by passing the working end of a
finished knot beneath the standing part and back around to the front; then cross the working end

in front and down through the loop you have just created (1, 2). In this way you form an overhand
knot (3) that will prevent the end of the main knot from slipping.